1. Field of the Invention
This invention relates to a hand-operable dispensing package for a viscous product such as a gel, a cream or a paste such as toothpaste. More particularly, this invention relates to a hand-operable dispensing package for a viscous product in which the product to be dispensed is contained within a cylindrical chamber and is dispensed from one end of the chamber under the influence of a pumping member at the one end in combination with a piston, usually referred to as a "follower piston", that moves within the chamber from the other end to the one end by virtue of partial vacuum conditions which are created within the chamber by the dispensing of the product.
2. Description of the Prior Art
U.S. Pat. No. 4,533,069 (J. L. Drobish) discloses a prior art hand-operable dispensing package for a fluid product in which the product is contained in a cylindrical portion of the package and is dispensed from a dispensing outlet at one end of the cylindrical portion under the influence of a hand-operable pumping element at the one end, in combination with an ambient air pressure operated follower piston that moves within the cylindrical portion from the other end to the one end. U.S. Pat. Nos. 4,474,313 (W. Sieverding); 4,564,130 (J. Eulenburg); 4,511,068. (J. Bossina) and 4,538,747 (A. von Schuckmann) disclose other dispensing packages of this general type. Packages of this general type have been used in the packaging of toothpaste and other high viscosity products. However, prior art dispensing packages for viscous products such as toothpaste are rather expensive, as the performance criteria for such packages, in terms of the reliability of dispensing the product and the reliability of sealing the package in a non-dispensing state, have heretofore been achieved by designs which are rather complex, in terms of the number of components of each such package or in terms of the complexity of one or more of such components. Further, such prior art dispensing packages have involved problems of refilling the portion of the container at the dispensing end with viscous product due to the resistance to flow of the viscous product within the container, which can lead to "suck back" of product into the container from the dispensing spout unless a check valve or similar obstruction to flow is provided.